I'm very fortunate to have both the A77 and A99, as far as sensitivity I think the full frame and more larger pixels make the A99 better in lower light. Also I shoot everything in RAW which gives me more options in low light conditions. Would even say the A99 is better in low light, up to 3200, than my A900.

But also faster lenses 50 1.4,24-70Z 2.8,70-200G 2.8 will allow for better low light shots. The 70-200G is my favorite lens for medium range, it's heavy and built like a tank. My 24-70Z is my favorite short lens.

My main issue w/A99 and A77 is the viewfinders, I've been spoiled by the A900 which I consider the best I have ever seen...

Will get to see how well the A99 performs this Weds. Night at our first night race at the drag strip.